It certainly depends on the preferences of the people involved. For most couples, actual penetration doesn't last that long -- usually less than fifteen minutes. When I have sex with my boyfriend, it probably lasts anywhere from five to fifteen minutes. Foreplay can take a lot longer, though!

It depends on the people, and how experienced you are. My boyfriend has learned to hold it for longer. but after you go... you can still keep going. don't worry about it, the more you stress yourself out about it the worse its going to be for you. just relax. its the best thing to do.

First-time sex can be amazingly short (like on the first stroke) or it might not happen at all if you are too nervous. Using condoms and masturbating before hand are techniques to increase your duration. Just try to be loving and sensitive. If you come too soon, try to continue pleasing her with touching or oral until you are ready to go for a second round. You do have to keep in mind that a lot of women have trouble reaching orgasm via intercourse, so if you can please her by other methods, it will be less of a concern if you don't last too long. Most girls, too, will understand that inexperienced guys may not last a long time. Just tell her she has you so excited that you simply can't help yourself. I think she will prefer that you orgasm too soon (meaning you find her sexy) that not being able to orgasm at all (meaning, too her, that she isn't sexy, even though the real reason is that you are paranoid about your performance to the extent you can't perform). Relax. It will all work out.